Resonance and criticality measure of ground motions via probabilistic critical excitation method     

Izuru Takewaki   《Soil Dynamics and Earthquake Engineering》2001,21(8):645-659

Resonant characteristics of recorded ground motions are investigated and a new measure of criticality of ground motions is proposed. Four classes of recorded ground motions, i.e., (i) near fault motions (rock records), (ii) near fault motions (soil records), (iii) long duration motions (rock records) and (iv) long duration motions (soil records), are taken from Abrahamson N, Ashford S, Elgamal A, Kramer S, Seible F, Somerville P, Proc of First PEER Workshop on Characterization of Special Source Effects, 1998. It is shown that resonant characteristics of recorded ground motions can be captured appropriately by means of the probabilistic critical excitation method due to the present author regardless of the type of ground motions and the distance between the critical response and the actual one can be a new measure of criticality of ground motions. The time-averaged approximate treatment of nonstationary ground motions as stationary ones is shown to be adequate for structures with shorter natural periods subjected to long duration ground motions.  相似文献   

太阳P模振动理论的研究     

毕少兰 《天文研究与技术》1999,(1):6

日震学是太阳物理的一个前沿分支学科,是根据太阳振动的观测来研究太阳的内部结构与运动的一种方法学。太阳５ｍｉｎ振动频率的理论计算和实测之间存在的显著偏差和振动模的激发问题一直是困扰日震学的两大难题,经过多年的研究仍然没有解决。然而太阳的表面层内绝热假设条件与真实情况有很大的偏差,我们认为绝大多数标准太阳模型的Ｐ模频率计算忽略了非绝热效应对频率的影响,忽略了振动的激发和衰减机制以及缺乏振动与对流湍流相互作用的知识。因此,我们必须发展非绝热理论来处理太阳５ｍｉｎ的振动问题  相似文献   

Seismic wave propagation in complex crust-upper mantle media using 2-D finite-difference synthetics   总被引：1，自引：0，他引：1  

S. O. Hestholm  E. S. Husebye  B. O. Ruud 《Geophysical Journal International》1994,118(3):643-670

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空间网格结构多维多点随机地震响应分析的高效算法   总被引：13，自引：0，他引：13  

薛素铎  王雪生  曹资 《世界地震工程》2004,20(3):43-49

将林家浩教授提出的“虚拟激励法”进一步推广应用于空间网格结构多维多点非平稳随机地震响应分析,推导了多维虚拟激励随机振动分析方法的理论公式,给出了峰值响应估计方法,并讨论了多维地震动的随机模型及参数选取,通过编制的专用计算机程序分析了网壳结构的随机地震响应。本方法自动包含了参振振型间及各输人地震分量间的相关项,计算精确、快速,非常适合分析频率密集型空间网格结构的随机地震响应,是一种高效的随机振动分析算法。  相似文献   

Wavelet‐based non‐stationary seismic rocking response of flexibly supported tanks     

Pranesh Chatterjee  Biswajit Basu 《地震工程与结构动力学》2004,33(2):157-181

The non‐stationary rocking response of liquid storage tanks under seismic base excitations including soil interaction has been developed based on the wavelet domain random vibration theory. The ground motion has been characterized through statistical functionals of wavelet coefficients of the ground acceleration history. The tank–liquid–foundation system is modelled as a multi‐degree‐of‐freedom (MDOF) system with both lateral and rocking motions of vibration of the foundation. The impulsive and convective modes of vibration of the liquid in the tank have been considered. The wavelet domain coupled dynamic equations are formulated and then solved to get the expressions of instantaneous power spectral density function (PSDF) in terms of functionals of input wavelet coefficients. The moments of the instantaneous PSDF are used to obtain the stochastic responses of the tank in the form of coefficients of hydrodynamic pressure, base shear and overturning base moment for the largest expected peak responses. Parametric variations are carried out to study the effects of various governing parameters like height of liquid in the tank, height–radius ratio of the tank, ratio of total liquid mass to mass of foundation, and shear wave velocity in the soil medium, on the responses of the tank. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Identification of base‐excited structures using output‐only parameter estimation     

Brad A. Pridham  John C. Wilson 《地震工程与结构动力学》2004,33(1):133-155

This paper presents a new identification technique for the extraction of modal parameters of structural systems subjected to base excitation. The technique uses output‐only measurements of the structural response. A combined subspace‐maximum likelihood algorithm is developed and applied to a three‐degree‐of‐freedom simulation model. Five ensembles of synthetically generated input signals, representing varying input characteristics, are employed in Monte Carlo simulations to illustrate the applicability of the method. The technique is able to circumvent some of the difficulties arising from short data sets by employing the Expectation Maximization (EM) algorithm to refine the subspace state estimates. This approach is motivated by successful application by previous authors on speech signals. Results indicate that, for certain system characteristics, more accurate pole estimates can be identified using the combined subspace‐EM formulation. In general, the damping ratios of the system are difficult to identify accurately due to limitations on data set length. The applicability of the technique to structural vibration signals is illustrated through the identification of seismic response data from the Vincent Thomas Bridge. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

An investigation of tuned liquid dampers equipped with damping screens under 2D excitation     

M. J. Tait  A. A. El Damatty  N. Isyumov 《地震工程与结构动力学》2005,34(7):719-735

This paper reports on the results of a study conducted on tanks partially filled with water, representing tuned liquid dampers (TLD), subjected to both 1D and 2D horizontal excitations. The sloshing response of the water in the tank is characterized by the free surface motion, the resulting base shear force, and evaluation of the energy dissipated by the sloshing water. A 1D non‐linear flow model capable of simulating a TLD equipped with damping screens is employed to model a 2D TLD. Application of this particular model requires the assumption that the response is decoupled and can be treated as the summation of two independent 1D TLDs. Results from the non‐linear flow model are compared with the 2D experimental shake table test results leading to a validation of the decoupled response assumption. This attractive decoupled response property allows square and rectangular tanks to be used as 2D TLDs, which can simultaneously reduce the dynamic response of a structure in two perpendicular modes of vibration. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Criteria for initiation of motion of rigid bodies to base excitation     

C. C. Tung 《地震工程与结构动力学》2005,34(10):1343-1350

It is known that when an unanchored rigid body is placed on a horizontal base which oscillates horizontally, it may undergo one of four modes of motion: rest, slide, slide–rock and rock. Initiation of a rigid body into these modes depends on the slenderness ratio of the body, the coefficient of friction between the body and the base and the acceleration of the base. In this study, the coefficient of friction and the base acceleration are considered random. For specific probability distributions of the coefficient of friction and the peak base acceleration, and for various values of the mean and standard deviation of the two random variables, the probabilities of occurrence of these modes of motion are obtained for a body of given slenderness ratio. It is shown that randomness of the coefficient of friction and base peak acceleration should not be ignored. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Study on the Sliding Displacement of a Sliding Structure Subjected to Multi-directional Earthquake Excitation     

FanAiwu TangJiaxiang LiLi YangJun 《中国地质大学学报(英文版)》2005,16(1):79-83

The investigation of sliding isolation is mainlyfocused on the response of a structure subjected to asingle directional earthquake excitation. Fan andTang (2001) studied the slide limited friction (S LF)base isolation system, using a sequential exponentialfriction model. Zhang and Cheng (2001) studied theisolated effect of a sliding bearing as a friction damp er. Xiong and Yu (2002) studied the numerical meth od of sliding isolation system. But studying a singlecomponent of e…  相似文献   

Dynamic analysis of train–bridge system subjected to non‐uniform seismic excitations     

He Xia  Yan Han  Nan Zhang  Weiwei Guo 《地震工程与结构动力学》2006,35(12):1563-1579

Based on the theory of dynamic wheel–rail interactions, a dynamic model of coupled train–bridge system subjected to earthquakes is established, in which the non‐uniform characteristics of the seismic wave input from different foundations are considered. The bridge model is based on the modal comprehension analysis technique. Each vehicle is modelled with 31 degrees of freedom. The seismic loads are imposed on the bridge by using the influence matrix and exerted on the vehicles through the dynamic wheel–rail interaction relationships. The normal wheel–rail interaction is tackled by using the Hertzian contact theory, and the tangent wheel–rail interaction by the Kalker linear theory and the Shen–Hedrick–Elkins theory. A computer code is developed. A case study is performed to a continuous bridge on the planned Beijing–Shanghai high‐speed railway in China. Through input of typical seismic waves with different propagation velocities to the train–bridge system, the histories of the train running through the bridge are simulated and the dynamic responses of the bridge and the vehicles are calculated. The influences of train speed and seismic wave propagation velocity on the dynamic responses of the bridge–vehicle system are studied. The critical train speeds are proposed for running safety on high‐speed railway bridges under earthquakes of various intensities. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献